This image from Horse Cave, Kentucky demonstrates how long stalactites can grow when combined into a single mass and undisturbed.
Anscocolor by Austin
The description states:
ONYX TAPESTRY, MAMMOTH ONYX CAVE, HORSE CAVE, KENTUCKY
The Only Tapestry depends between the cave chambers like a curtain shielding the entrancing scenes beyond, from the prying eyes of the visitor.
–The errant comma is in the original. This image is one that can easily be mistakenly viewed inverted, as lighting comes from below, which is not the expected direction. This card dates from the 1950s.